1. Field
The disclosed concept relates generally to electrical switching apparatus and, more particularly to electrical switching apparatus, such as circuit breakers. The disclosed concept also relates to shaft assemblies.
2. Background Information
Electrical switching apparatus, such as circuit breakers, as well as transfer switches, network protectors and the like, are often equipped with accessories such as, for example and without limitation, auxiliary switches, shunt trip devices, under voltage release devices, and bell alarms. Such devices can be employed in a variety of ways to provide signals indicating certain conditions within the apparatus and/or to initiate a change in status of the apparatus such as, for example, to trip open the separable contacts of the apparatus in response to an electrical fault condition (e.g., without limitation, current overload; short circuit; abnormal voltage).
Some of these accessories include an actuator, such as a stem or plunger, that is movable from a retracted position to an extended position in which it is structured to engage and actuate (e.g., pivot) a corresponding shaft assembly (e.g., without limitation, trip bar; D-shaft) associated with the circuit breaker operating mechanism. Accordingly, it will be appreciated that such shaft assemblies can be employed in cooperation with a wide variety of different accessories to facilitate circuit breaker operations.
Typically, the trip bar or D-shaft is pivotally supported by bearings, with an end of the shaft extending through and beyond one of the bearings such that it is cantilevered with respect thereto. The cantilevered end of the shaft includes a number of protrusions (e.g., without limitation, paddles) extending radially outwardly from the shaft. Each actuator (e.g., without limitation, stem; plunger) of the aforementioned accessories engages and moves a corresponding one of the paddles in order to pivot the shaft and initiate the desired circuit breaker operation. Among other disadvantages, such shaft assemblies are reliant upon strict, difficult to achieve tolerances with respect to shaft assembly components, and relatively minimal misalignment among the assembly components can cause the shaft assembly, and thus the circuit breaker, to not function properly.
There is, therefore, room for improvement in electrical switching apparatus, such as circuit breakers, and in shaft assemblies therefor.